Method of making prosthesis



June 21, 1949. Y A. A. NELSON 2,473,723

METHOD OF MAKING PROSTHESIS Filed NOV. 5, 1945 4 Sheets-Sheet 1 R n Y u m m NF R 8/ we m o 4 3 M I. A Y /Q!n r B H 5 NM 0 L .A 9 G 2 I 2 m 5 2/ IIII\ lll. lllli w Huh l I M l o l\1 uu y A? A W I /0. Z V 3 a June 21, 1949. A. A. NELSON 2,473,723

METHOD OF MAKING PROSTHESIS Filed Nov. 5; 1945 4 Sheets-Sheet 2 INVENTOR Ale A l ve/son BY 3123M ATTORNEY.

June 21, 1949. A. A. NELSON 2,473,723

METHOD OF MAKING PROSTHESIS Filed Nov. 5, 1945 4 Sheets-Sheet 3 gwomq bob A/ex Ne lsoo June 21, 1949. A, NELSON 2,473,723

METHOD OF MAKING PROSTHESIS Filed Nov. 5, 1945 4 Sheets-Sheet 4 Alex zLNe/son Patented June 21, 1949 METHOD OF MAKING PROSTHESIS Alex A. Nelson, Pleasant Ridge, Mich.

Application November 5, 1945, Serial No. 626,791

4 Claims.

My invention pertains to the production of prosthesis or the making of artificial body members, and for such purposes it may be regarded as an improvement on the invention disclosed and claimed in my copending patent application Serial No. 619,279, filed September 29, 1945.

This invention relates to the production of artificial prosthesis such as fingers, hands, arms, toes, feet, legs, ears, noses, breasts and such other lost parts to the human anatomy as desired. It is very simple in its processing and results in tough, durable, flexible prosthesis; has a lifelike, skinlike feel, appearance and texture. Heretofore it has been necessary to create this prosthesis as a solid object or if a lighter article was desired, it was necessary to introduce internal cores into the mold to make them hollow when using synthetic resins or soft rubber. These procedures and the materials have proven unsatisfactory. Slush type castings of latex rubber have been used to some extent for the creation of these hollow prosthesis. The ensuing hollow rubber article is then painted with suitable paints, varnishes or lacquers to simulate skin color. This procedure is also very unsatisfactory, first, because of the opaqueness of the finished article; second, because the latex rubber shrinks about 30% within six months of its construction; and third, the latex rubber turns progressively dark brown with the result that the appearance of the prosthesis turns darker. This change of color plus the 30% shrinkage makes it necessary to have a new appliance made in less than six months.

It is accordingly an object of this invention to eliminate these drawbacks to artificial prosthesis,

and to make possible the construction of lifelike and practically undetectable substitutes for parts of the human anatomy.

It is also an object of my invention to provide improved artificial flexible body members which are more natural and lifelike having improved accuracy of size, color and texture as well as improved permanence of size, color and flexibility.

It is also an object of my invention to provide improved flexible hollow artificial body members which may be more strongly and permanently attached to other materials and elements such as control members.

It is a further object of my invention to provide an improved process for making hollow artificial body members without the use of internal cores.

Another object of my invention is to provide an improved method of forming and coloring artificial body members to produce a more faithful reproduction of the amputated body member to be replaced.

The invention itself, however, both as to the process and the product, together with additional objects and advantages thereof, will best be understood from the following description when read in conjunction with the accompanying drawings, in which:

Fig. 1 is an elevational view showing the two halves of a split mold for reproducing a human hand;

Figs. 2, 3 and 4 are elevational views showing how the material is spread over the inner surfaces of the mold;

Fig. 5 is an elevational view representing the application of the color pigments to the coating previously formed on the surfaces of the mold;

Fig. 6 is an elevational view showing the two halves of the mold clamped together for receiving thinned material poured thereinto;

Fig. 7 is an elevational view showing the removal of the thinned material;

Fig. 8 is an elevational view of the product;

Fig. 9 is a sectional view on line 99 of Fig. 8 and greatly enlarged;

Fig. 10 illustrates one step of my improved method of making an exceptionally faithful mold of a hand, and shows the wax cut ofi of the back of the hand;

Fig. 11 shows a wax palm impression trimmed away;

Fig. 12 shows a wax palm section in position and strapped on wrist of a subject with adhesive tape preparatory to making back of hand impress1on in wax;

Fig. 13 shows how the material deposited on the palm section is stripped away;

Fig. 14 shows both palm and back sections, with lugs added to the wax impressions, preparatory to immersion into dental casting investment material;

Fig. 15 is a cross-sectional view showing back of hand wax impression invested in dental investment material before dissipation of the wax by heat;

Fig. 16 is a perspective view showing a wrist p;

Fig. 17 is a perspective view showing the application of crease or line color into the palm of the mold; and

Fig. 18 is a similar view showing how the molding material is applied over the surfaces of the cavities in the mold sections.

Referring more specifically to the Fig. 1 of the drawing, it will be seen that I provide a split mold having two halves H and I3 between which is formed a cavity in the shape of a hand with the wrist portion thereof opening from the upper side walls of the mold. These two halves of the mold may be formed in simulation of the hand to be reproduced by the well known methods of copying and reproducing and, as will be apparent, one of the halves H may have the cavity simulating the palm and front half of the hand while the other half I3 has a cavity which simulates the back of the hand.

Previously to make these prosthesis, it was necessary either to sculpture or shape wax, or other suitable material, into the desired form of the lost part or parts (we are to replace) of the human anatomy, and the sculpturing or shaping of material to make a model is satisfactory only insofar as an ear, a nose or a breast replacement is concerned. When it comes to hands, fingers, toes,

feet, etc., I have found it best to duplicate an existing form from nature by means of an impression, and from such impressions, in wax or other suitable materials, the sections of the mold may be made up by well known methods. However, I have devised an improved method for making molds for this purpose which are exceptionally faithful copies of the member to be reproduced, and which will be disclosed in detail, subsequently.

We are now ready to-make the prosthesis and it will be a hollow prosthesis, for purposes of description.

At the present time, the most satisfactory materials for this use are the synthetic resins of the vinyl family designated as resins in solution or suspension. More specifically, the material may comprise a base of either vinyl chloride, vinylidene chloride, vinyl chloride-vinylidene chloride, or vinyl chloracetate to which has been added as plasticizers dioctyl phthalate, dibutyl phthalate and/or butyl phthalyl butyl glycollate. These three plasticizers can bev used individually but are preferably used in combination, equal quantities of each, and simply mixed together with regular and usual apparatus and by proper heat treatment these are brought to the proper consistency.

In making prosthesis where a multiplicity of colors have to be used, these materials are colored basically previous to bringing them to the desired puttylike consistency. However, after they have been brought to the proper puttylike consistency, they are still subject to being modified with modifying pigments in a highly satisfactory manner. 1

The patient for whom the prosthesis is being made is called in and test color batches are made to match the various portions of his good left hand-such as line and groove colors on back of knuckles, palm of hand, wrist, and under side of fingers, finger tip color, nail color, palm mound color, vein color, heel of thumb color, heel of palm color, overall palm color, overall back of hand color, and knuckle color and any freckles, blemishes or scars it is desired to reproduce.

At the time the wax impression was made, individual impressions of each finger nail was made in plaster of Paris. These impressions are now used to make hard finger nails which will be inserted into the metal mold. The procedure is as follows: vinyl resin sheeting of .010" or .015" thickness is cut into suitable squares of a size to cover the individual nail impressions. Placing the sheet of clear resin over the nail impression, both are then placed into an oven of approximately 175 degrees Fahrenheit and left until the resin sheeting becomes limpid soft. A piece of cotton pressed against the limpid sheet resin forcing it into the depression of the nail and holding it for a few minutes until cool gives an outline of the nail in the resin sheet which can then be removed from the plaster mold and trimmed with a pair of shears to this outline. The nail, when trimmed, is then inserted into its respective position in the metal mold l3, cemented to position with a cellulose base or other type of cement. This procedure is carried out until all the nails have been completed and cemented to position in the metal mold. Moons are painted on the nails with material that has been colored the correct color for this purpose. A thin line of the material is also placed around the finger tip edge of the nail.

The proper back-of-nail color material is then applied to each nail and then, on the palm section mold, I I, finger tip color is applied and smoothed down. The creases on the under side of the finger joints andthe lines in the palm of the hand appear as ridges in this metal mold. The summits of these ridges are now painted their proper shade of red or pink with a very thin, narrow line. The mounds in the palm of the hand which correspond to the reverse of the knuckles are now filled in with the selected mound color. The heel of the thumb color is placed in and the under side of the thumb itself is laid down with its color. The heel of the palm is colored properly and then the overall palm color is blended into these other layers by means of a moistened finger or instrument, and smoothed to the desired thickness and contour, carrying the material to the full length of the wrist or arm. This color application is also shown in Fig. 17. The plastic forming material is preferably inserted as a lump or gob 29 on upwardly positioned wrist surfaces of the cavity, as represented in Fig. 2. From this position it is more readily spread as a coating over the remainder of the cavity surfaces, progressively, as represented by the horizontal shade lines in Figs. 3 and 4.

The material is brought up slightly above the parting line or edge of the mold allowing the material to slightly lap over onto the parting edge for approximately of an inch. This may be also seen in Fig. 18. This section of the mold is then set aside momentarily.

The back of the hand section I3 is now placed in position for working. The ridges on the joints 7 of the finger (ridges in this metal mold but depressions or creases in the actual fingers) are painted on the summits with a thin, narrow line of color of the desired shade of red or pink. The same may be done with the knuckles on the back of the hands. Then with a fine, pointed instrument, fine dots or specks of brown, sun tan, red and/or pink are speckled over the back of hand and wrist and arm portions of the mold. These specks should be placed irregularly. The vein material isnow placed in position, after having been modified to suit the individual case, as regards color. It is so placed as to follow the vein depressions apparent in the mold. These will be found to extend from the arm or wrist to midway between the knuckle and second joint of the fingers and in some cases lapping over on the under side of the thumb. They are also apparent on the underside of the wrist. The knuckle color is then laid down and shaped for each knuckle, not forgetting the wrist joint knuckle. Any scars on the hand are outlined with. the proper colored material. The molding material of the proper amazes basic skin tone, previously selected and modified if necessary, is then applied and smoothed to shape over the entire back .of the hand, and blended at the edges where necessary. By heating the mold sections to about 150 Fahrenheit, the applicationof the .material 'is :tacilitated. The material is brought up slightly-above the surface of the mold separation and overlapping :it about & of an inch. Vein and other colors are then applied over the coating, as .per vertical shade lines, in Fig. 5.

Halves of the mold are-now placed into apposition with one another, :the clamping screws 23 placed in position through the lugs 2-! and the surfaces brought into apposition :by tightening. To insure accurate alignment, two holes '2 are drilled .in the two moldsections H and [3 in opposite aligned relation near thewvrist portion. A pin or screw 25 is then .secured .in the hole in .the back section, and another projection12lis secured in the hole in the palmsection H ,Leach projecting as a pilot member into the aligned hole .in the other part. .Fig. 1 shows .thesecooperative holes 24 and pins 25 and 27!.

In order to assure positive union of all the seams, it is well for the .novice to mix .up a slushing fluid material which is made .by using the skintone shade that was used for the back of the hand, or for that matter, the one .used 'for the overall palm color can be used for this purpose. This material is placed in a cup and sufiicient plasticizer, either dioctyl phthalate or buty'l :phthalal butyl glycollate is added and thoroughly .mixed until a fluid readily pourable liquid is secured. Holding the mold in an upright position withthe wrist section up, this liquid material ispoured intothe mold and swished around so that the seams are well coated, allowed to stand a moment and then turned upside down and .allowed to drain out. When drained, the wrist .cap opening of the .mold is closed by a cover or in any suitable manner.

Some of the puttylike material, regardless of color, in fact it can be scrap or leftover material mixed together is taken and formed over the outside seams of the mold, being sure to cover all of the seams with a layer about T 6 of an inch-thick and extending each side of the seam about of an inch.

The method of curing can be one of the following two: first, glycerine or other suitable liquid is heated to 295 degrees Fahrenheit and the mold placed in the glycerine which is maintained at this temperature -for five to seven minutes, depending upon the thickness of the mold as well as of the thickness of the hand we are making (that is to say if the hand were a solid one, it would take correspondingly longer at this temperature to cure the mass through). At a lower temperature, a longer period of time is necessary but at no time should the temperature be below 2'75 degrees and the time necessary would be approximately twenty minutes. A higher temperature can be used and at '310 degrees approximately three minutes is all that is required. Ihave .found that a temperature of 295 degrees in the glycerine bath gives me excellent results. .As the temperature is increased, the tensile strength of the material is improved but "the temperature must not be such as to fatigue the pigments nor the light and heat stabilizers used. This can be readily understood since vinyl resins are extremely heat sensitive at around 250 degrees Fahrenheit and turn to a yellowish color grcwing iprogressively purplish brown and ultimately black when ,sub-

ject to temperatures above .250 degrees Fahrenheit without good heat and light stabilizers.

Second, dry heat can'be used, and .in :instances where this is done, it is necessary to have a thermometer well incorporated into the mold and extending to within e of an inch of, or better still, to come in actual contact with the material in the mold. This thermometer well must be so placed in-the mold, and themold so placed in the oven, that the thermometer will protrude through anopening in theoven so the thermometer can be readily read from outside the oven. The oven is brought to a temperaturerof "10 to 15 degrees above what we desire the cure to .be and held at that temperature for ten or fifteen minutes. The mold is then placed therein, observing the precaution as noted regarding the thermometer and the oven rheostat turned down to the desired temperature. The cold mold will dra the temperature down slightly in absorbing the heat. The mold is then kept in the oven until the thermometer within the mold registers the desired temperature and held there for the desired time. To insure an accurate reading of the thermometer within the mold, it is necessary, when placing the thermometer within the thermometer well, to protect it from the fluctuating rises of temperature of the oven. This is done by placing some of the flexible material in puttylike form into the well and letting it extend up onto the thermometer above the well.

When the material has cured for the proper length of time, it is removed from either the liquid loath or the oven and it can be cooled by immersion into cold water. The clamping screws and nut removed, the mold disassembled andthe prosthesis removed. It is washed with soap and water and any internal mechanisms that allow for opening and closing are inserted and attached to the bucket and the mechanism assembled, the patient called in and the appliance attached.

It should have been stated in the above paragraph that when the prosthesis is removed from the mold, any seams or rather any flash at the seams, trimmed off with sharp shears, dental burs or rotary files or coarse stones until smooth and seam obliterated. Ethyl acetate is then applied to a piece of coarse toweling and rubbed onto the seams just treated until smooth.

In order to make the prosthesis more lifelike in .its appearance, hair is inserted into the prosthesis in the following .manner.

Asewing needle is placed into a pin vise with the eye extending outward. The eye is cut through with an abrasive stone until a U-shaped pronged stem is left. Hair from a babyshead-or a young child is then secured of the proper color to match the hair on the goodhand, and cut into lengths of about 1% to 2 inches. Alength of hair is placed on the back of the hand of the prosthesis and with the pronged instrument made from the needle straddling the middle of it, it is forced into the prosthesis at an angle. It is given a slight twist and the instrument removed. This is continued over theback-of theghand, wrist and fingers until suflicient hair is placed to match the hair pattern on the good hand. The hair is trimmed witha pair of curved manicure shears to desired length.

What has been described .for .a complete ihand holds .good for .a finger, group .of fingers, .etc.

.The steps of the .process accordingly comprise briefly:

1. Provide a split mold in simulation of the member to be reproduced, as represented in Fig. 1, for example.

2. Heat the mold, to say about 150 F.

3. Take one part of the heated mold, say the front half, paint proper color pigments upon certain portions and apply a gob 29 or lump of the molding material, which is of a rather soft puttylike consistency, and place it in the upper portion of the mold on the cavity surface, as shown in Fig. 2.

4. By means of a lubricated finger or any suitable implement spread the material out over the entire surface of the cavity forming a skin like coating, perhaps about A; inch thick. This is represented by horizontal shade lines applied progressively in Figs. 3 and 4.

5. Various color pigments are then applied representing veins and the various natural colors and color irregularities seen in a human hand. This is represented by vertical shade lines in Fig. 5.

6. Take the other half of the heated mold, the back half of the hand, and after insertion of pieces of hard material representing the finger nails, treat it as in paragraphs 2, 3, 4 and 5.

7. Put the two halves of the mold together fitting snugly in proper cooperative relation.

8. If desired, take some of the same material in a suitable vessel and thin it with a suitable vehicle or solvent.

9. Pour the thinned material into the mold through the wrist opening, as represented in Fig. 6. In a short time pour it out, as represented in Fig. 7. A portion will remain coated on the previously applied material and the central portion will pour out leaving a central cavity.

10. Close and place the mold into an oven and cure the material at a temperature and for a time suitable for the material. This may be at temperatures between 250 and 350 F. for 1 to 20 minutes. This operation also seals the two parts of the prosthesis together. The immersion of the mold into a glycerine bath at 295 F. and kept there for 5 to '7 minutes is preferred to the dry oven cure.

11. Remove the formed hand from the mold and trim up any flash material.

12. Adjust any internal mechanism and apply to the patient. In many types of internal mechanisms, it is preferable to place the mechanism before closing the mold and baking.

Prosthesis made by my improved process are more natural and life like and have improved accuracy of size, color and texture, as well as improved permanence of size, color and flexibility. In the finished product 32, as represented in Fig. 9, there may be a plurality of coatings, in a laminated relation, comprising an outer coating 33 enclosing and attached to an inner coating 35. Color pigment 31 is shown entrapped permanently between the coatings. Also color may be applied on the exposed surfaces as disclosed.

However, in order to provide a mold which is very accurate and faithful, and which is of light weight requiring a minimum of metal, I have devised the following process. The patient who has suffered the loss let us say of the right hand presents himself for an impression of his left hand. This is taken in plaster of Paris, or other suitable impression material, well known to those allied to the dental profession and to some extent to mold and model makers. This impression is then cast in artificial stone, plaster of Paris, or other suitable material and when separated from the impression, a model of the patients left hand ensues. The patient is dismissed and with the model of his left hand a search is conducted through observation and comparison among different people who have a left hand that resembles this model hand in size, shape and outstanding contours. When such an individual is found, an impression of his right hand, and as much of the arm as is desired, is made in the following manner:

1. Parafine wax of 133 to 135 degrees melting point is melted in a tall, narrow metal container of sufiicient depth to allow the individual to thrust his hand into the fluid wax for the depth desired to secure the total impression. The container is usually about twelve to thirteen inches in depth and about seven inches in diameter. The parafine wax is allowed to cool so that when a thermometer is placed in the center of the mass, it registers not more than 128-129 degrees.

2. The hairs on the individuals right hand are shaved off and as high up on the arm as it is desired to secure an impression. The hand is cleaned of all moisture and standing erect with his hand at his side in a natural position, with very little space between the fingers, the patient dips his hand into the vessel containing the wax slowly, and removes it slowly. He allows the surface of the wax to slightly harden. After this is done, if the patient desires to remove the heat more rapidly, he can thrust his hand in a bucket or vessel of cold water and the heat simply leaves his hand. All Water is then removed from this surface of coated wax on the patients hand. He then continues to successively thrust his hand into and remove it from the molten wax and allowing it to cool until he has made approximately twenty-one dips which gives a satisfactory thickness to the mold, Fig. 10, wax is then removed from the back of the hand and above the height of contour, being careful not to remove the wax 4! from around the wrist, or the wrist portion of the arm for about the depth of an inch. This wax is left so as to retain the palm section 43 of the wax in its proper position, while the wax is being removed from the back of the hand and the back of the fingers and the thumb. After having removed sufficient of the wax from the back of the hand and fingers and thumb, the hand is then thrust into a pail of ice water and held until the wax is thoroughly chilled and stiff. The wrist section on the back of the wrist and arm is then cut away above the height of the contour, and the hand gradually teased out of the wax impression. The wax section 43, now known as the palm half of the mold, Fig. 11, trimmed down to the height of contour of the hand and, at the finger tip portion, it is so trimmed that any detail of the finger nails is obliterated since we want all detail of finger nails in the top half of the mold. The splines or walls of wax between the fingers are trimmed down carefully to the height of contour of the fingers. The outside edge is then trimmed so it presents a well defined, broad, fiat surface to make a mold edge. That section between the thumb and first finger is then trimmed down and so tapered upward from the thumb and the side of the thumb nail so a slight taper exists, going upward toward the index finger. It may be necessary to bring the edge of the mold onto the inner surface of the index finger in order to get a good draw of the mold.

When this has been accomplished and smoothed so it is apparent to the eye that a good draw of the upper half can be made, the under or back surface of this wax palm section of mold is then filled in with wet cotton or tissue paper to obliterate alI hollows existing.'- Parafine wax is then painted over this wet tissue paper or cotton and luted to the edges of this waximpression' so as to hold itin'pla'ce. Colored wax, black or green orany s'uitablec'olor, is then tracedon thisunder' surface asnear to the outside edge as possible'so-as to afiord a guide for the successive steps in making the impression of the back of the'hand', fingers and thumb. The outside of this section is the'npainted with oil of sweet almond or lanolin smeared over the entire under surface and onto the edges of the splines and allowed to slightly overlap ontothe intaglio surfaceof this palm section.

When this has been accomplished. thispalm section 43 then is replaced in position on the hand ofthe'patient; taped to position-with adhesive tape M at the-upper portion of the wrist or arm as in Fig. 12. Thehand assumes its natural position at the side of the individualand is thendipped into" the parafine wax which has been heated and again cooledto approximately 128 degrees Fahrenheit.- Successive dips are made and allowed to cool between each dipping, in much the-same fashion as candles are dipped, until approximately 21- clips have been made. The wax on the under surface of the palm sectionitha't is', the wax' from the new dippings that have" now encased the palmsection, are cut away, keeping well under. where the edge of the: two" halves of this-wax impression would come;- and' which is readily discernible. The wet tissue paper or cotton is lifted from the under side of the palm section, and the wax cut away around the outside borders until we appreach the colored wax designating the edge of the palm section of the mold. The/hand is then plunged into ice cold water and held until the wax on the back of the hand is chilled through, and has become hard and stiff. The adhesive tape which held the palm section in place on the wrist and arm is then cut and removed from both the under side or the palm section of the mold and from the back of the arm. Any overhanging edges of the wax from: the back of the hand section that prevent easy separation of the two halves of this wax impression are removed, and the hand replaced in the cold water, and the patient instructed to gently try to flex his hand to effect a separation of the two halves of the mold, as shown in Fig. 13.

When separated, the patient is dismissed.

After noting carefully that the two halves 43 and 45 of the mold have not been distorted and will go into place properly, these wax impressions are then wiped dry and lugs 2| of wax attached at convenient places on both sections of the mold in apposition to one another so as to form a means whereby a wing nut screw can be placed through them to hold the two surfaces of the tobe-finished mold together.

These wax impressions are now placed in a bath of water containing a surface tension reducer, or wetting agent, such as for instance- Nacconol. This treatment makes the wax wet so that the investment material to which it will be subject adheres to it and reproduces all the fine detail.

Normally, wax is water repellent and this wetting agent treatment is necessary in order to pour investment around it to secure detail.

These wax impressions now become our pat terns for making a metal mold and after the wetting agent treatment, an investment material of which there are a great number, and of which ing.

thedental profession and allied industries there to. are acquainted with,;ispoured onto the intaglio surfaces and the entire mass of wax completely enclosed with the. investment material 41 held in' a suitable' container, such as a tin can or metal'fiask d-Sz: Investment material of sand, silica; or pumice and: plaster of Paris can be mixed readily and inexpensively, or prepared ones onthe market can-be used. Each half of the wax impression is individually fiasked or invested in this manner.

The wrist and arm portion ofthe wax impression or pattern that is being invested will" naturally be at the top of the mix and this will become, when the wax hasbeen boiled out,v the pouring sprue;

After the investment material has set, the mass containing: the investment and" wax pattern is placed in boiling water and boileduntil the-parafine wax is eliminated from the mold of investment material. The mass of investment material is then placed in an oven and heat applied, approximately 200*degrees, for a' few hours and then the temperature raised to approximately 300-325 degrees Fahrenheit,.and held for such time as to completely dehydrate the mold of investment material. This usually takes about 19 hours. To ascertain' whether the mold is completely dehydrated; it is merely necessary to take a mirror-like piece of metal, or a glass mirror, that-is, cool or coldand place it at the opening of the mold of investment material. If moisture is present within the mold. a vapor will appear on-this mirror-like surface of metal or glass. When no moisture is present..- there will be no vapor, and then th'e'mold' is ready for cast- Printers: type metal ofsuitable grade or tin-- smiths 50/50 solder is then heated until it is melted and poured into thev investment mold. The mold is allowed to stand after pouring for about five or six hours, preferably over night so asto insure an undisturbed crystallization of the mass of material poured therein; When cool, the mold i'splaced in water and the investment gradually softens and is readily washed away from the metal casting 5! which is an exact duplicate of the Wax impression that we took of the patients hand.

When both sections of the mold have been cast, they are cleansed with water, soap and a brushand dried and the two halves of the mold assembled to make sure the parts are in perfect apposition to one another.

Holes are drilled in lugs 2! that were provided at convenient opposite places for receiving clampin screws therethrough of proper length and diameter to clamp and hold the two parts of the mold into apposition to one another. Held clamped together in proper position, the wrist portion of the assembled mold is then cut with a hacksaw flush so that the two halves of the mold are approximately the same length. The outside edges of the metal at the wrist is then shaped to allow for a slight taper extending upward toward the arm. A piece of wax approximately n in thickness and of proper width and length is then adapted over this end section of the wrist or arm, lapping it over aproximately an inch, pressing it to shape, chilling it, withdrawing it and giving it the bath treatment with the wetting agent, a pouring sprue attached and invested in a suitable sized vessel or can. When set, the wax is boiled out and when dehydrated, cast with type metal or 50/50 solder. When 11 cooled, it is removed from the investment, cleansed and placed in position on the assembled mold.

In addition to the clamping lugs 2|, additional cooperative pilot means may be provided, as previously described, for assuring an accurate alignment of the two parts of the mold. A cap 53, shown in Fig. 16, is provided for covering and closing the wrist opening of the assembled mold sections.

After cleaning, the mold can be hard chromium plated, if desired, and the sections are utilized in accordance with my process for making prosthesis, as previously described.

In some instances it may be desired to make a mold of white artificial stone, a thin layer reinforced with a heavy layer of a zirconium type investment material (used to cast chromium alloy and stainless steel) in place of the metal mold. The zirconium investment allows a rapid heat penetration. The stone is used for smooth detail.

It is apparent that within the scope of my invention modifications and variations may be made other than herein disclosed, and the present disclosure is illustrative merely, the invention comprehending variations thereof.

I claim:

1. The method of making hollow artificial body members for prosthesis which consists in, providing a split mold having cooperative cavities between the two parts of the mold and opposed faces forming sharp mold replicas of the natural surfaces for prosthesis in simulation of the memher to be copied and opening from one side of the mold, heating the mold up to about 150 F., spreading over the cavity surfaces of the mold a plasticized puttylike vinyl plastic material which tends to flow as it is heated, applying color pigments upon the interior surface of the coating so formed in simulation and configuration of veins, blemishes and other natural features corresponding to the surface replica, positioning the two parts of the mold snugly together with the cavities thereof in cooperative relation and the opening upward, pouring into the mold some of the vinyl plastic material thinned with a suitable vehicle and forming therewith a backing interface entrapping the pigmented features of the interior, pouring such thinned material out of the hollow article thus formed, subjecting the mold to heat of about 250-350 F. for curing and seal- 12 ing the molded article, and opening the two parts of the mold apart for removing the molded memher.

2. The method of making artificial body mem bers in accordance with claim 1 and said material being a vinyl resin with plasticizer from the group consisting of dioctyl phthalate, dibutyl phthalate and butyl phthalyl butyl glycollate.

3. The method of making hollow artificial body members in accordance with claim 2 in which the plasticizer consists of about equal parts of the three members of the group, and the curing is at about 295-310 F.

4. The method of making an artificial body member for prosthesis consists in, preparing a split mold of the body member to be replaced in which the mold faces delineate sharply by ridges the creases and folds of a skin surface to be copied, applying color to the ridges, warming the mold and pressing into the mold configurations so as to embed the color in creases a putty-like coat of thermoplastic vinyl resin containing plasticizer, applying color to the interior face of the vinyl coat in representation of natural color characteristics of the member, then forming an interface back of the interior color by flowing thereover to build up a film vinyl resin thinned with solvent, removing excess thinned resin from the film thus formed, then curing the resulting hollow resin article at about 250-350 F., to form a prosthesis closely simulating the light-reflecting properties of a natural body member.

ALEX A. NELSON.

REFERENCES CITED The following references are of record in the file of this patent:

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